Communications networks are formed from an interconnection of network switch equipment over communications channels. The communications channels include a variety of physical implementations using radio, optical, and electrical signalling. With increasing frequency, network implementations provide differing communications technologies operating over one communications channel. For example, electrical communication over telephone outside plant can include analogue telephone signalling, or plain old telephone service (POTS) and digital data signalling, also referred to as digital subscriber line signalling. Even within a class or category of communication, such as digital data signalling, there are many forms of signalling which are supported and governed by a respective standard promulgated by a standards body recognised in the industry. There are divergent requirements placed on communication networks to transport particular types of traffic on a circuit switched, that is connection based or fixed bandwidth communications paradigm, or packet switched, that is connectionless or traffic based communications paradigm. These include the transport of data, streaming real time audio and visual data streams as well as traditional plain old telephone service voice traffic. Consequently there are a diversity of networks each of which is standards driven that increase the complexity of providing a network infrastructure to support the increasing traffic loads and expanding protocol universe resulting in ever-increasing demands on network operators and carriers to stay current while supporting legacy communication systems.
Intelligent optical networking is driving new network architectures in both the metro and core of the network to support these communications demands. An emerging protocol that provides interoperability between connection based and connectionless communications is multi-protocol label switching (MPLS). MPLS is an example of a technology that permits bridging the asynchronous transfer mode (ATM) and the Internet protocol (IP) network architectures. Communications over a network requires delivery of data from a source to a destination, which is the function of the network switch to provide. Within a network switch, traffic is routed from an ingress point to an egress point. Traffic switching can occur at more than one location of a switch, for example within the switch core or fabric or at the switch line card level, which interconnects the switch to the communication network channels.
In a communication switch, ingress and egress forwarders or line cards require routing information for every destination address in a communication network. As the communication network adds and loses connections to other communication elements, the routing information changes and this is a dynamic circumstance of network traffic and a consequence of adding or removing nodes and links to the network. The routing information is frequently stored locally in memory in the ingress and egress line cards. The routing information is provided to each line card from a central location in the communication switch. As the number of line cards in a communication switch increases, the task of downloading the routing information to each line card requires more bandwidth and processing resources of the communication switch.
In the past, a central routing processor in a router with multiple forwarders, for example an IP routing processor, updates routing tables used by the forwarders. In the embodiment, each forwarder is located on a respective line card. The central routing processor accesses a central table of routes and transmits routing updates from this table to the forwarders to update their respective routing tables. The forwarders are accessed in sequence to update their routing tables. A forwarder may become too busy to respond resulting in delay. Updating proceeds one forwarder at a time at a rate for each forwarder that corresponds to its capabilities and load. The total time to update N forwarders is N times the average update time for the group of forwarders. Where route updates are constantly being made due to network traffic flows and other dynamic considerations such as additions of network nodes and links, the total time to update imposes limits to scalability by introducing traffic overhead inefficiencies, routing errors and retry attempts.
There is a need for a system and method that can efficiently provide the routing information from the central location to the line cards.